Method and apparatus for improving antenna efficiency

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application is a continuation-in-part application of U.S. patent application Ser. No. 10/412,371, entitled “Antenna”, to Chadwick, filed on Apr. 11, 2003, now U.S. Pat. No. 6,891,512 which is a continuation-in-part application of U.S. patent application Ser. No. 09/724,535 entitled “In-Vehicle Exciter”, to Chadwick, filed on Nov. 27, 2000 now abandoned and U.S. patent application Ser. No. 10/160,747, entitled “Exciter System and Excitation Methods for Communications Within and Very Near to Vehicles”, to Chadwick, et al., filed on May 30, 2002, now U.S. Pat. No. 6,600,896 and the specifications thereof are incorporated herein by reference.

0002This application claims priority to Japanese Patent Application Serial No. 2003-116664, entitled “Antenna Device”, filed on Apr. 22, 2003, and the specification thereof is incorporated herein by reference.

BACKGROUND OF THE INVENTION

00031. Field of the Invention (Technical Field)

0004The present invention relates to an antenna device that improves the Transmit/Receive (T/R) efficiency characteristics of an antenna by improving the signal to noise (S/N) ratio in the radio communications.

00052. Description of Related Art

0006Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.

0007Currently, antennas used in wireless LAN, GPS, TV, etc, are typically single-use antenna with frequency bands ranging from MHz, to tens of GHz. Since frequency band (wavelength range) is determined by use, these antennas are designed to be tuned to a specific frequency. For example, IEEE802.11b (wireless LAN), uses a 2.4 GHz band frequency. Reduced Transmit/Receive (T/R) efficiency of single-use antenna can result in limited receiving areas and thus require greater transmitting power.

0008Since, discone type antennas have the outstanding characteristic of broadband capabilities, it is possible that one antenna may be used for multiple services. However, the discone's gain is lower than a single-use antenna, to date, this has prevented the practical use of discone type antennas for multiple uses.

0009The practical use of discone type antennas for multiple services can result if the T/R efficiency is improved. This would have a dramatic affect on personal services such as wireless LAN, GPS, etc since they could all be presented with just one antenna.

0010Conventional antennas, which are used for a specific wavelength, such as the ¼-wavelength grounded antenna, do not always have a sufficient S/N ratio. If the S/N ratio is improved, it will become possible to reduce the transmission power or, likewise, to increase the receiving distance.

0011Since the discone type antenna is typically used for broadband T/R frequencies, using a discone type antenna for a specific wavelength results in a reduced S/N ratio, when compared with other antennas.

0012Various technologies have been developed to improve the S/N ratio, such as, electromagnetic wave radar equipment with improved reliability, which allows only a fixed frequency, for Transmitting and Receiving, to pass efficiently, thus controlling the influence of noise. See Japanese Patent Publication No. 11-248835 entitled “Radio Wave Radar Apparatus”.

0013Such radar is equipped with an antenna for Transmitting/Receiving an electromagnetic wave, as well as a shield conducting component that is grounded and covers the antenna of the radar unit. The shield component has a screen for frequency selection in the area facing the antenna. The screen is comprised of a conductive film having multiple holes uniformly arranged in two dimensions. The size and arrangement of the holes are chosen to allow a selected frequency to pass through. This selected frequency is the maximum allowed to pass. The screen, intercepts the noise of frequencies lower than the selected frequency. This screen part can be comprised of multiple conductive films, with holes, arranged in piles. The screen part may also be comprised of a mesh conductive wire, or a conductive film having multiple parallel slits etc.

0014Japanese Patent Publication No. 01-305606 entitled “Antenna Device with Radome”, describes a device consisting of an antenna and a grounded radome that protects the antenna from its natural environment. The radome also provides frequency selectiveness.

0015Japanese Patent Publication No. 09-083238 entitled “Antenna System for Multi-Wave Common Use” describes an antenna device for multi-waves that can be made smaller by modifying the shape of the discone type antenna.

0016U.S. patent application Ser. No. 10/412,371 entitled “Antenna”, U.S. patent application Ser. No. 10/160,747 entitled “Exciter System and Excitation Methods for Communications Within and Very Near to Vehicles” and U.S. patent application Ser. No. 635,402, entitled “In-Vehicle Exciter”, which are incorporated herein by reference, disclose a modified discone exciter, which is used for communications within a vehicle. The present invention is applicable to modified discone type antennas, as well as other types of antennas.

BRIEF SUMMARY OF THE INVENTION

0017The present invention is directed to the enhancement of antenna efficiency. The invention preferably comprises an antenna, a non-grounded conductive object, and an insulated space lying between the antenna and the non-grounded conductive object. The antenna used in the invention is preferably a discone type antenna comprising a disc, a cone comprising an apex and a base comprising a diameter, with the disc positioned at the apex of the cone, and a feed wire preferably disposed in an interior of the cone and extending outwardly beyond the cone.

0018The non-grounded conductive object preferably comprises an aluminum or copper material. The material can be substantially flat, but is preferably curved. The curve can be simple, substantially spherical, or cylindrical in nature. A curved non-grounded conductive object comprising an angle of between approximately 60 degrees and approximately 180 degrees is preferred. The thickness of the non-grounded conductive object is preferably less than or equal to approximately ten millimeters in thickness.

0019The non-grounded conductive object can comprise a double wall. The interior of the double wall may be hollow or can have some insulative material, such as plastic, disposed therein.

0020The non-grounded conductive object may, but preferably does not, completely enclose the antenna.

0021The insulated space preferably comprises air, however, plastic or any other insulative material may be used. The insulated space is preferably less than or equal to approximately 50 millimeters in thickness.

0022The present invention also relates to a method for improving antenna efficiency. In the preferred embodiment, a non-grounded conductive object is placed in a particular position proximate the antenna. A discone type antenna, as discussed above is preferably utilized. The preferred non-grounded conductive object is the same as that discussed above.

0023A primary object of the present invention is to improve the efficiency of antennas.

0024A primary advantage of the present invention is that signal to noise ratio in antennas, including those currently in use, is improved in an efficient and cost effective manner.

0025Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

0026The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings:

0027<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view showing the preferred embodiment of the present invention where the discone type antenna is partially surrounded by a curved non-grounded conductive object;

0028<figref idref="DRAWINGS">FIG. 2</figref> is a perspective drawing of the current invention showing an open-ended, cylindrical, non-grounded, conductive object, wherein the disk of a discone type antenna has been placed at the opening of the non-grounded conductive object;

0029<figref idref="DRAWINGS">FIG. 3</figref> is a perspective view showing the antenna completely within a cylindrically shaped, open-ended, non-grounded, conductive object;

0030<figref idref="DRAWINGS">FIG. 4</figref> is a perspective view showing the antenna partially exposed from the open-ended, non-grounded, conductive object;

0031<figref idref="DRAWINGS">FIG. 5</figref> is a schematic cross section view showing the non-grounded conductive object, placed so as to create sidewalls and a canopy for the antenna;

0032<figref idref="DRAWINGS">FIG. 6</figref> shows an example in which the non-grounded conductive object is curved partially around the antenna;

0033<figref idref="DRAWINGS">FIG. 7</figref> is a schematic cross section view showing a thick non-grounded conductive object;

0034<figref idref="DRAWINGS">FIG. 8</figref> shows an example in which a non-conductive substance is encased within a double-walled non-grounded conductive object;

0035<figref idref="DRAWINGS">FIG. 9</figref> shows a substantially spherically shaped non-grounded conductive object;

0036<figref idref="DRAWINGS">FIG. 10</figref> is a cross section view of a discone type antenna;

0037<figref idref="DRAWINGS">FIG. 11</figref> is a description view of a discone type antenna;

0038<figref idref="DRAWINGS">FIG. 12</figref> is a detailed drawing of the antenna device depicted in <figref idref="DRAWINGS">FIG. 13</figref>;

0039<figref idref="DRAWINGS">FIG. 13</figref> is a schematic measurement arrangement view of an implementation of the present invention;

0040<figref idref="DRAWINGS">FIG. 14</figref> is a chart showing the measurement result of electromagnetic wave intensity;

0041<figref idref="DRAWINGS">FIG. 15</figref> is a graph showing the change in S/N ratio when the non-grounded conductive object is applied;

0042<figref idref="DRAWINGS">FIG. 16</figref> is a graph showing the S/N ratio as distance is varied, for the current invention in the embodiment, shown in <figref idref="DRAWINGS">FIG. 1</figref>, as well as two prior art antennas;

0043<figref idref="DRAWINGS">FIG. 17</figref> is a graph showing the signal power, in dBm, received by the current invention as well as two prior art antennas, as distance is increased from the transmitter;

0044<figref idref="DRAWINGS">FIG. 18</figref> is a graph showing the S/N for the Melco antenna without a non-grounded conductive object;

0045<figref idref="DRAWINGS">FIG. 19</figref> is a graph showing signal and noise readings for the Melco antenna without a non-grounded conductive object;

0046<figref idref="DRAWINGS">FIG. 20</figref> is a graph showing the signal range for the Melco antenna without a non-grounded conductive object;

0047<figref idref="DRAWINGS">FIG. 21</figref> is a graph showing the S/N for the discone type antenna with a curved non-grounded conductive object added;

0048<figref idref="DRAWINGS">FIG. 22</figref> is a graph showing signal and noise measurements for the discone type antenna with a curved non-grounded conductive object added;

0049<figref idref="DRAWINGS">FIG. 23</figref> is a graph showing the signal range for the discone type antenna with a curved non-grounded conductive object added;

0050<figref idref="DRAWINGS">FIG. 24</figref> is a graph showing signal and noise readings for the PC card with no external antenna;

0051<figref idref="DRAWINGS">FIG. 25</figref> is a graph showing the signal to noise ratio for the discone type antenna with a curved non-grounded conductive object added; and

0052<figref idref="DRAWINGS">FIG. 26</figref> is a graph showing signal and noise readings for the Melco antenna without a non-grounded conductive object.

DETAILED DESCRIPTION OF THE INVENTION

0053The present invention is directed to antennas, particularly to those having broadband capabilities, which with improved Transmit/Receive (T/R) efficiency, can result in one antenna being used to T/R the numerous frequency bands of multiple services.

0054The terms “antenna” and “electromagnetic wave resonance part” are used interchangeably throughout the specification and are intended to mean a system for sending and receiving electromagnetic waves and to generate or produce an electric field. The term “discone” is intended to mean a particular type of antenna or electromagnetic wave resonance part, having disc and cone components, and this term is also intended to cover “disc-cone” or other such exciters having this configuration. In both the claims and the description, the term “substantially flat” is meant to encompass not only those surfaces that are generally flat, but also those surfaces that are flat.

0055The present invention is an antenna device having an electric wave resonance portion of an antenna and a non-grounded conductive object. The object lies in a particular position proximate the antenna. An insulated space lies between the antenna and the object. The non-grounded conductive object can completely or partially enclose the antenna, and should not be electrically connected to the antenna.

0056While not completely understood, it is believed that the signal to noise ratio is improved by the present invention because a potential similar to static induction is formed by an interaction with the electromagnetic wave in the non-grounded conductive object when placed in a particular position proximate the electromagnetic wave resonance part of the antenna, thus creating an electromagnetic wave interference function which tends to attenuate noise.

0057Various kinds of antennas are applicable for the present invention, and an improvement of the T/R efficiency, especially for multiband antennas, has substantial benefits. The discone is one example of a multiband antenna. Since the discone type antenna is capable of very wide bandwidth it can be used for various services, such as FM/AM radio, digital TV, GPS, Wireless LAN, RKE (Remote Keyless Entry), GDO (Garage Door Openers), cellular phones, and PHS (Personal Handy phone Systems).

0058The following is a description of the basic structure and operating characteristics a discone type antenna relying on J. J. Nail's, <i>Designing Discone type antennas, Electronics, </i>August 1953, PP167-169.

0059The schematic cross section view of discone type antenna <b>40</b>, of the present invention, is shown in FIG. <b>10</b>. Discone type antenna <b>40</b> comprises disk <b>42</b>, cone <b>44</b>, feeding cable <b>46</b> and central conductor <b>48</b> of feeding cable <b>46</b>. Electric power is fed to disk <b>42</b> through central conductor <b>48</b> of feeding cable <b>46</b>. The cone <b>44</b> is typically grounded.

0060The design parameters of a discone type antenna are shown in FIG. <b>11</b>. C<b>1</b> is the maximum diameter of cone <b>44</b>, C<b>2</b> is the minimum diameter of cone <b>44</b>, L is the slant height of cone <b>44</b>, Φ is the flare angle of cone <b>44</b>, S is disk-to-cone spacing, and D is the diameter of disk <b>42</b>.

0061The bandwidth of a discone type antenna can be determined by evaluating its Standing Wave Ratio (SWR). Frequencies in which the SWR is less than 2 are referred to as the bandwidth of the antenna. The lowest frequency of the discone's bandwidth has a wavelength of approximately 4 times the slant height of the cone.

0062Using a cone flare angle (Φ) of 60 degrees can result, according to Nail, in a discone antenna with a bandwidth from 400-1300 MHz or more. It is possible to reduce the minimum frequency of the bandwidth by increasing diameter C<b>1</b> of cone <b>44</b>. Decreasing space S between disk <b>42</b> and cone <b>44</b> can increase the maximum frequency of the bandwidth.

0063<figref idref="DRAWINGS">FIG. 1</figref> shows the preferred embodiment of the current invention. As shown therein, a discone type antenna is used with a curved non-grounded conductive object <b>20</b>. The curve may have any magnitude of curvature, however, a non-grounded conductive object with a smaller, rather than greater, magnitude of curvature is preferred. A curve of about 60 to about 180 degrees is preferred.

0064While any conductive substance can be used, it is preferred that the non-grounded conductive object is of aluminum or copper formed into in a curved shape. A thickness of about ten millimeters or less is preferred for the non-grounded conductive object. While holes may be placed in the non-grounded conductive object, this is not the preferred embodiment. A non-grounded conductive object having a height greater than the antenna is preferred, however, a non-grounded conductive object having a height less than the antenna also yields desirable results. A mounting base can be used to dispose the non-grounded conductive object to a number of surfaces and objects.

0065In the preferred embodiment the insulative material, which lies between the non-grounded conductive object and the antenna, is air, however, plastic or any other insulative material may be used in other embodiments of the present invention.

0066The present invention is preferably used in conjunction with a broadband antenna, such as a discone type antenna.

0067<figref idref="DRAWINGS">FIG. 2</figref> shows an embodiment of the present invention wherein the disk of the discone type antenna is placed at the opening of the non-grounded, open-ended, cylindrically shaped, conductive object <b>20</b>.

0068Another embodiment of the present invention is shown in FIG. <b>3</b>. The antenna device <b>10</b> is comprised of electromagnetic wave resonance part <b>12</b> of an antenna and non-grounded conductive object <b>20</b> placed near electromagnetic resonance part <b>12</b>. Antenna feeding part <b>14</b> is attached to electromagnetic wave resonance part <b>12</b>. Electromagnetic wave resonance part <b>12</b> is disposed inside non-grounded conductive object <b>20</b>. Non-grounded conductive object <b>20</b> has a shell-like wall <b>24</b> that surrounds the upper portion and sides of electromagnetic wave resonance part <b>12</b>. Opening <b>22</b> is located at the bottom of the non-grounded conductive object <b>20</b>. Wall (shell) <b>24</b> of non-grounded conductive object <b>20</b> is separated from electromagnetic wave resonance part <b>12</b> by air or another insulator.

0069<figref idref="DRAWINGS">FIG. 4</figref> is another example of antenna device <b>10</b>. In this example, electromagnetic wave resonance part <b>12</b> is partially exposed under non-grounded conductive object <b>20</b>.

0070In <figref idref="DRAWINGS">FIGS. 5-7</figref>, schematic cross section views of various embodiments of the present invention are shown. Other examples of non-grounded conductive object <b>20</b> are shown in <figref idref="DRAWINGS">FIGS. 8 and 9</figref>.

0071<figref idref="DRAWINGS">FIG. 5</figref> shows an example of non-grounded conductive object <b>20</b> wherein wall (shell) <b>24</b> is in the shape of a rectangular parallelepiped and acts as sidewalls and canopy for electromagnetic wave resonance part <b>12</b>.

0072<figref idref="DRAWINGS">FIG. 6</figref> shows an example in which non-grounded conductive object <b>20</b> is curved partially around electromagnetic wave resonance part <b>12</b>.

0073<figref idref="DRAWINGS">FIG. 7</figref> shows an example of antenna device <b>10</b> in which non-grounded conductive object <b>20</b> is thick.

0074<figref idref="DRAWINGS">FIG. 8</figref> shows an example in which a non-conductive substance <b>28</b> is encased within double-walled, non-grounded, conductive object <b>20</b>. While <figref idref="DRAWINGS">FIG. 8</figref> shows wall <b>24</b> on the inside and outside of non-conductive substance <b>28</b>, it is also sufficient to place wall <b>24</b> only on the inside or outside of non-conductive substance <b>28</b>.

0075<figref idref="DRAWINGS">FIG. 9</figref> discloses another embodiment of the present invention, wherein non-grounded conductive object <b>20</b> is substantially spherically shaped. However, it is also possible to completely enclose an antenna within a non-grounded conductive object.

0076The non-grounded conductive object <b>20</b> of the present invention, equipped with a conductive wall (or shell) <b>24</b>, can generate induced current or an electric charge. The non-grounded conductive object <b>20</b> of the present invention is not grounded. The electric charge or current generated by the electromagnetic wave contacting the non-grounded conductive object <b>20</b> is confined in the wall (shell) <b>24</b>, of the present invention.

0077Generally, if an antenna is covered by a conductive substance and this conductive substance is grounded, the inside can be shielded against external electromagnetic waves. The shielding effect is substantially different from that achieved by the present invention. The purpose of shielding is to protect the antenna from electromagnetic waves. The present invention increases the T/R efficiency by placing a non-grounded conductive object near the antenna. This results in an improved signal to noise ratio.

0078The present invention is suitable for radio communication systems, especially for wireless LAN with GHz band frequencies as well as systems utilizing the broadband characteristic of a discone type antenna. The present invention is suitable for antennas that reside on vehicles, buildings, airplanes, and satellites, as well as those used for cell phones and digital television signals.

0000Industrial Applicability:

0079The invention is further illustrated by the following non-limiting examples.

EXAMPLE 1

0080A schematic measurement arrangement view depicting an experimental setup is shown in FIG. <b>13</b>. Transmitting equipment <b>100</b> was equipped with transmitting circuit part <b>102</b> and transmitting antenna <b>104</b>. Receiving equipment <b>120</b> was comprised of antenna device <b>10</b>, receiving antenna part <b>122</b>, and receiving circuit part <b>124</b>. Receiving circuit part <b>124</b> had an Automatic Gain Control (AGC) function built into it which stabilized the output signal.

0081<figref idref="DRAWINGS">FIG. 12</figref> shows a detailed drawing of the antenna device depicted in FIG. <b>13</b>. Antenna device <b>10</b> was composed of discone type antenna <b>40</b> and non-grounded conductive object <b>20</b>. Insulative part <b>26</b> of non-grounded conductive object <b>20</b> was filled with insulator <b>26</b>. Discone type antenna <b>40</b> was placed on insulating base <b>52</b>, and feeding part <b>46</b> of discone type antenna <b>40</b> was extended outside through base <b>52</b>.

0082In <figref idref="DRAWINGS">FIG. 13</figref>, the circuit of an IEEE 802.11b communication system (2.4 GHz band) was used as transmitting equipment <b>100</b>, and a card with an external output-terminal of the communication system was used as receiving equipment <b>120</b>.

0083In this example, a 2.4 GHz discone type antenna was used in conjunction with a non-grounded conductive object which was a rectangular parallelepiped (aluminum foil lining) with inner dimensions (ID) of 8 cm×8 cm×10 cm (height). The discone type antenna was so disposed that the perpendicular centerline of it and the center of the non-grounded conductive object coincided.

0084<figref idref="DRAWINGS">FIG. 14</figref> is a chart depicting time on the horizontal axis and electric wave intensity on the vertical axis. The graph shows the dramatic affect in noise and signal to noise measurements at the moment the non-grounded conductive object was applied. As can be seen in <figref idref="DRAWINGS">FIG. 14</figref>, though the signal output remained virtually unchanged, the noise was reduced by 10 dBm. As a result, S/N ration was improved.

EXAMPLE 2

0085In the schematic measurement view of this experiment, shown in <figref idref="DRAWINGS">FIG. 13</figref>, a sine wave signal from 50 MHz to 30 GHz was generated from transmitting circuit part <b>102</b>, then utilizing this signal, an electromagnetic wave was generated from discone type antenna <b>104</b> having a cone slant height of 3.8 cm and a cone flare angle of 60 degrees. The receiver employed another discone type antenna of the same shape and size as that used for the transmitter. The received electromagnetic wave's power was measured using a spectrum analyzer.

0086Two different non-grounded conductive objects were tested. Non-grounded conductive object A was cylindrically shaped, having a diameter of 25 cm and a height of 10 cm. Non-grounded conductive object B was also cylindrically shaped, however, its diameter was 8 cm with a height of 10 cm. Both of the conductive objects were made of aluminum. These conductive objects were then placed over the antenna and their effects recorded. These results are shown in FIG. <b>15</b>. In <figref idref="DRAWINGS">FIG. 15</figref>, the horizontal axis shows frequency and the vertical axis shows signal to noise ratio in dB. One can see that for frequencies of less than approximately one GHz non-grounded conductive object A provides a better signal to noise ratio, however, for frequencies that are greater than approximately one GHz. the S/N ratio for non-grounded conductive object B is greater than that of A.

EXAMPLE 3

0087The S/N ratio was measured while varying the shape, material, and size of the non-grounded conductive object, using the same setup described in example 1. Results of this experiment are shown in Table 1.

0088<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 1</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>S/N Readings Obtained From Different Conductive Object Materials,</entry></row><row><entry>Shapes, and Thicknesses</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="offset" colwidth="21pt" align="left" /><colspec colname="1" colwidth="161pt" align="center" /><colspec colname="2" colwidth="35pt" align="center" /><tbody valign="top"><row><entry /><entry>Non-grounded conductive object</entry><entry /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="6"><colspec colname="1" colwidth="21pt" align="left" /><colspec colname="2" colwidth="35pt" align="left" /><colspec colname="3" colwidth="35pt" align="left" /><colspec colname="4" colwidth="42pt" align="center" /><colspec colname="5" colwidth="49pt" align="center" /><colspec colname="6" colwidth="35pt" align="center" /><tbody valign="top"><row><entry /><entry /><entry /><entry /><entry>Thickness</entry><entry>Change in</entry></row><row><entry>No.</entry><entry>Material</entry><entry>Shape</entry><entry>I.D. (cm)</entry><entry>(mm)</entry><entry>S/N (dB)</entry></row><row><entry namest="1" nameend="6" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="6"><colspec colname="1" colwidth="21pt" align="left" /><colspec colname="2" colwidth="35pt" align="left" /><colspec colname="3" colwidth="35pt" align="left" /><colspec colname="4" colwidth="42pt" align="center" /><colspec colname="5" colwidth="49pt" align="char" char="." /><colspec colname="6" colwidth="35pt" align="char" char="." /><tbody valign="top"><row><entry>Ex.</entry><entry>aluminum</entry><entry>rectangu-</entry><entry>8 × 8 ×</entry><entry>0.3</entry><entry>10</entry></row><row><entry>3-1</entry><entry>foil</entry><entry>lar para-</entry><entry>10 (h)</entry></row><row><entry /><entry /><entry>llelepiped</entry></row><row><entry>Ex.</entry><entry>Aluminum</entry><entry>cylinder</entry><entry>25φ × 10 (h)</entry><entry>1</entry><entry>2</entry></row><row><entry>3-2</entry></row><row><entry>Ex.</entry><entry>Steel</entry><entry>cylinder</entry><entry>15φ × 17 (h)</entry><entry>1</entry><entry>5</entry></row><row><entry>3-3</entry></row><row><entry>Ex.</entry><entry>Aluminum</entry><entry>rectangu-</entry><entry>22 × 17 × 14</entry><entry>30</entry><entry>1.5</entry></row><row><entry>3-4</entry><entry /><entry>lar para-</entry><entry>(h)</entry></row><row><entry /><entry /><entry>llelepiped</entry></row><row><entry>Ex.</entry><entry>Brass</entry><entry>cylinder</entry><entry>15φ × 17 (h)</entry><entry>0.5 (diameter</entry><entry>5</entry></row><row><entry>3-5</entry><entry /><entry>1 mm</entry><entry /><entry>of brass wire)</entry></row><row><entry /><entry /><entry>mesh</entry></row><row><entry>Ex.</entry><entry>Polyethyl-</entry><entry>cylinder</entry><entry>15φ × 17 (h)</entry><entry>0.2</entry><entry>0</entry></row><row><entry>3-6</entry><entry>ene</entry></row><row><entry namest="1" nameend="6" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

EXAMPLE 4

0089The same setup was used as in Example 1, except that the S/N ratio was measured while raising the non-grounded conductive object above the discone type antenna. However, almost no change was noticed, even when part of the discone was exposed from the lower end of the non-grounded conductive object.

EXAMPLE 5

0090The same setup was used as in Example 1, except that an ordinary antenna for IEEE 802,11b system (2.4 GHz band) was used instead of the discone type antenna. A rectangular parallelepiped of 8 cm×8 cm×10 cm (height) was used for the non-grounded conductive object. This resulted in a 2 dB improvement in the Signal to Noise ratio.

EXAMPLE 6

0091Using the setup depicted in <figref idref="DRAWINGS">FIG. 13</figref>, three different antennas were tested. The first, labeled <b>11</b><i>b</i>, was the standard personal computer (PC) card having only its internal antenna and no external antenna. The second set of measurements made, labeled as Melco, were obtained by applying an external antenna, made by Melco, to the standard PC card of the first measurement (<b>11</b><i>b</i>). No conductive object was used in conjunction with the first two measurements. The third antenna used was similar to that depicted in <figref idref="DRAWINGS">FIG. 1</figref>, a discone type antenna having a curved non-grounded conductive object placed near it. Each receiving antenna was initially located next to the transmitter antenna. Each of the three receiving antennas was then moved to a distance of 230 meters from the transmitter, with multiple measurements of both S/N ratio and received power taken along the way. The results of these measurements were then plotted in graphs FIG. <b>16</b> and FIG. <b>17</b>. Based on these graphs it is evident that the non-grounded conductive object resulted in a sizable increase not only in the received signal power, but also in the S/N ratio.

EXAMPLE 7

0092The setup described in Example 6 was used. Maintaining a constant non-varying distance from the transmitter to the receiver, measurements for each of the three antennas were taken. These measurements consisted of signal, noise, signal to noise ratio, and signal range. The results of these measurements are depicted in <figref idref="DRAWINGS">FIGS. 18-26</figref>.

0093<figref idref="DRAWINGS">FIG. 22</figref> shows signal and noise readings obtained from a discone antenna with a curved non-grounded conductive object. Comparing the graph of this antenna with that of the Melco antenna (having no conductive object) and the PC card (also having no conductive object) with no external antenna (<figref idref="DRAWINGS">FIGS. 19 and 24</figref> respectively), a definite advantage of the present invention can be seen. While the noise for each averaged around −90 dBm, the signal reading for the discone type antenna with a curved non-grounded conductive object averaged signal readings of about 10 dBm greater than the two antennas that had no conductive objects. These results are repeatable as evidenced by <figref idref="DRAWINGS">FIGS. 25 and 26</figref>, which show the same results produced from the same setup but taken at a different time.

0094S/N readings for the Melco antenna, with no conductive object, and the discone type antenna, having a curved non-grounded conductive object, are shown in <figref idref="DRAWINGS">FIGS. 18 and 21</figref> respectively. Looking at these readings, an increase in the S/N of approximately 10 dBm is readily detectable for the discone type antenna having a curved non-grounded conductive object. <figref idref="DRAWINGS">FIG. 20</figref> shows the signal range for the standard Melco antenna, while <figref idref="DRAWINGS">FIG. 23</figref> shows the signal range for the discone type antenna with a curved non-grounded conductive object. Based on these graphs, one can see that not only is the signal of the discone antenna, with the non-grounded conductive object, higher, but it also has less variation with time, hence an antenna with a non-grounded conductive object produces a smother signal.

0095Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.